I've been fiddling with the valve and it seems to produce the most foam when the water level is just below the 4" opening. Hard to describe.... See pic.

This morning there was about a 6" tall tube of nasty brownish/green foam sticking out of the tee.

And Ethan, if the air dome is on it traps the surface water and the opposite corner of the pond from the skimmer I'll get some foam after a few hours with the bottom drain running. But with the air dome off I don't have any foam around the two returns and they're somewhat violent in how the water comes back.... So maybe there's just not enough DOC's to get the results I see pictures of?

Still quite happy with it.

Grant

Grant, I have 16 fish in 5500 gallons (which could be closer to 5,000), and they range from 12 inches to 27 inches. Most are in the 15-20 inch range, estimated at 45-50 lbs of fish. I feed 5-6 times a day, my water temp is between 85-88 right now. I have a huge oak tree (neighbor) that when it rains, it runs down the leaves and into the pond....so, I constantly have doc issues. Yet, this works well to constantly pull out foam.

You have the water level right where it should be....just below the opening to the tee. putting the unit in shade helps, high humidity helps, low wind helps, more docs help, etc....but just know that no matter what...if you get docs, you have a perfect way to extract them.